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Small interfering RNA (siRNA), sometimes known as silencing RNA, is a class of double-stranded RNA molecule that interferes with the expression of specific genes.

Site visit

A visit by agency officials, representatives of the sponsor, or consultants to the location of a research activity (e.g. a clinical trial site) to assess if the site is fully prepared for the protection of trial participants and the safe and successful conduct of the clinical trial.

Small Interfering RNA

Small Interfering RNA

Soft Endpoint

The endpoint in a clinical trial is an event such as occurrence of a disease, or symptom, or a particular laboratory result. Once someone reaches the endpoint, they are generally excluded from further research in the trial.

A soft endpoint is a subjective measure. For example, it is common to measure quality of life as an endpoint in Phase III trials, with patients asked specific questions about the impact of their disease and/or treatment.

In contrast, a hard endpoint is an endpoint that is well defined and can be measured objectively. For example in cancer research, the endpoint in a trial might be related to response to treatment (such as shrinkage of a tumour).

The endpoints used in a trial must be defined and documented as part of the trial design.


The ability of a substance (solute) to permanently dissolve in liquid to form a homogeneous solution.


The term somatic is often used in biology to refer to the cells of the body, in contrast to the germ-line cells which usually give rise to the eggs or sperm. In medicine, it is a term that means (more generally) relating to the body. Somatic mutations are changes to the genes which are not passed on to the offspring. In cancer genetics, somatic mutations specifically refer to mutations arising in tumours (which are not present in healthy tissue). Such mutations are often responsible for driving the growth of tumours.

Somatic Cell Nuclear Transfer

In genetics and developmental biology, somatic cell nuclear transfer (SCNT) is a laboratory technique for creating an embryo from a body cell and an egg cell. The technique consists of taking an egg cell lacking the nucleus and implanting a donor nucleus from a body cell. It is used in both therapeutic and reproductive cloning.

Somatic-cell therapy medicine

A somatic-cell therapy medicine contains cells or tissues that have been manipulated to change their biological characteristics, and subsequently reintroduced into patients. These cells or tissues can be of autologous, allogeneic, or xenogeneic origin (cells obtained from a donor of a different species). The aim with somatic-cell therapy is to cure, diagnose, or prevent diseases.


Specificity (of an assay or test) is the ability of an experiment or trial to correctly detect only the particular effect being studied “ for instance, a difference in symptoms between two groups of participants receiving different medicines in a clinical trial. If a trial is not specific enough, it will give a false positive result (Type I error).


The sponsor is the individual, company, institution or organisation which takes responsibility for the initiation and management of a clinical trial. The financing of a clinical trial may come from the sponsor, but can also come from a third-party. The organisation of a clinical trial is particularly complex because important aspects of the trial are not under the direct control of the sponsor.

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